Push-button switch apparatus having cam actuated switch contacts and selective illumination means

ABSTRACT

A pushbutton switch apparatus having pushbuttons which are selectively illuminated when their rear ends are pushed through openings in a shutter plate into a depressed position adjacent one of a plurality of light outputs of a light guide member coupled to a single light source. The switches have movable contacts and stationary contacts fixedly attached to an etched circuit board and operated by cam actuators on the push buttons. The shutter plate includes leaf spring shutter doors over the openings to prevent the light from entering the undepressed pushbuttons and provide better contrast. The light pipe is provided with a plurality of branches having inputs of different areas which increase in area with the distance of their outputs from the light source to provide more uniform brightness of the illuminated pushbuttons.

United States Patent [72] inventors Anthony E. Sprando;

Peter S. Winkelmann, both 01 Portland, Oreg.

[21] Appl. No. 831,589

[22] Filed June 9,1969

[45] Patented June 8, 197! [73] Assignee Tektronix Inc.

Beaverton, Oreg.

[54] PUSH-BUTTON SWITCH APPARATUS HAVING CAM ACTUATED SWITCH CONTACTS AND SELECTIVE ILLUMINATION MEANS 11 Claims, 4 Drawing Figs.

[52] US. Cl... 200/167 [51] Int.Cl Hillh 9/18 [50] Field of Search 200/167 A,

5 E, 169 PB [56] References Cited UNITED STATES PATENTS 3,163,739 12/1964 Hutt 200/164(A) 3,169,506 2/1965 Morris ..200/l67(A)(X) 3,305,677 2/1967 Bov ..200/l67(A)(X) 3,336,456 8/1967 Ploetz 200/l67(A) Primary Examiner-41. 0. Jones Attorney-Buckhorn, Blore, Klarquist and Sparkman ABSTRACT: A pushbutton switch apparatus having pushbuttons which are selectively illuminated when their rear ends are pushed through openings in a shutter plate into a depressed position adjacent one of a plurality of light outputs of a light guide member coupled to a single light source. The switches have movable contacts and stationary contacts fixedly attached to an etched circuit board and operated by cam actuators on the push buttons. The shutter plate includes leaf spring shutter doors over the openings to prevent the light from entering the undepressed pushbuttons and provide better contrast. The light pipe is provided with a plurality of branches having inputs of different areas which increase in area with the distance of their outputs from the light source to provide more uniform brightness of the illuminated pushbuttons.

PUSH-BUTTON SWITCII APPARATUS HAVING CAM ACTUATED SWITCII CONTACTS AND SELECTIVE ILLUMINATION MEANS BACKGROUND OF THE INVENTION The subject matter of the present invention relates generally to pushbutton switch apparatus and in particular to such an apparatus having cam actuated switches whose movable contacts are fixedly attached to an etched circuit board and having illumination means for selectively illuminating the pushbuttons upon depression through openings in a shutter plate into a position adjacent one of the outputs of a light guide member.

Cam actuated switches having movable contacts fixedly attached to a printed circuit board have several advantages including a better high frequency response due to the lower lead inductance, as disclosed in copending U.S. Pat. application Ser. No. 765,597 of H. Vollum et al. Pushbutton switches have previously been employed to actuate switches whose movable contacts engage stationary contacts on a printed circuit board, as shown in U.S. Pat. No. 2,853, 565 of Arthur et al. However, the pushbutton switch apparatus of the present invention differs from such prior switch apparatus by employing pushbuttons to operate cam actuated switches of the Vollum type.

In addition, the pushbutton switch apparatus of the present invention also has the advantage of providing an improved illumination means whereby a plurality of pushbutton members are, upon actuation, selectively illuminated with a more uniform brightness and higher contrast with respect to the unactuated pushbuttons in a simple, inexpensive manner, by means of a single light bulb and associated light guide. Thus, conventional pushbutton switch apparatus employ a separate light bulb for illuminating each pushbutton, as shown in U.S. Pat. No. 3,271,530 of Wirsching. It has previously been proposed in U.S. Pat. No. 2,440,063 of Andrews to selectively illuminate a plurality of pushbuttons by means of a single light source by moving the pushbuttons into alignment with apertures in a masking plate, but this gives a nonuniform brightness to the illuminated pushbuttons due to their different distances from the light source and causes reduced contrast due to the leakage of light into the unactuated push buttons. While this latter problem was solved to some extend in U.S. Pat. No. 3,290,473 of Goldbeck et al., it still uses a plurality of light sources to prevent the nonuniform illumination of the pushbuttons, with such light sources being positioned between the pushbuttons and resulting in a bulky and more expensive construction. These disadvantages have been overcome by the illumination means in the apparatus of the present invention.

In addition, the present invention provides an extremely compact pushbutton switch apparatus of low cost and reliable operation which has a long, useful life up to 100,000 operations per switch. The pushbutton switch apparatus is easy to construct and repair. Its illuminated pushbuttons indicate which switch is operated over a wide viewing angle, and have a unifonn high brightness and good contrast. Furthermore, the cam actuated switches of the present apparatus have low lead inductance and an extremely good high frequency response. Thus the pushbutton switch apparatus may be used in electronic instruments having a wide frequency bandwidth, such as cathode ray Oscilloscopes, computers, and digital voltmeters.

It is therefore one object of the present invention to provide an improved pushbutton switch apparatus of inexpensive, compact construction which has a long useful lifetime.

Another object of the invention is to provide an improved pushbutton switch apparatus of reliable operation which is easy to repair.

A further object of the present invention is to provide an improved pushbutton switch apparatus providing selective illumination of the pushbuttons with a uniform brightness and good contrast.

Still another object of the present invention is to provide an improved pushbutton switch apparatus for operating cam actuated switches whose fixed and movable contacts are attached to a printed circuit board to provide such switch apparatus with low inductance and an extremely high frequency signal response.

BRIEF DESCRIPTION OF DRAWINGS FIG. I is an oblique elevation view of one embodiment of the pushbutton switch apparatus of the present invention;

FIG. 2 is a front elevation view taken along the line 2-2 of FIG. I;

FIG. 3 is a section view taken along the line 3-3 of FIG. 1 with parts broken away for clarity; and

FIG. 4 is a section view taken along the line 4-4 of FIG. 3 with parts broken away for clarity.

DESCRIPTION OF PREFERRED EMBODIMENT One embodiment of the pushbutton switch apparatus of the present invention is shown in FIG. 1 and includes a plurality of pushbutton members 10 which are made of light conducting material, such as the transparent polycarbonate plastic sold under the name LEXAN, to enable light to be transmitted therethrough. The ends 12 of the pushbutton members are provided with a roughened surface for light diffusion, so that such end surfaces are illuminated when the pushbuttons are depressed into light coupling relationship with a light guide member 14, in a manner hereafter described. The pushbuttons 10 extend through openings in the front of a housing 16 of light opaque plastic material and are supported in a straight line to form a row of pushbuttons, as shown in FIG. 2.

As shown in FIGS. 3 and 4, each of the pushbutton members 10 operates a switch actuator member 18 of insulating material, such as the acetyl resin DELRIN, having a pair of cam surfaces 20 separated by a ridge 22 which functions as a spacer and guide. Each of the cam surfaces 20 engages at least one movable leaf spring contact 24 of a cam actuated switch attached to an etched circuit board 26. The switches include fixed switch contacts 28 provided by metal strips on the sheet of insulating material forming the circuit board. In the preferred embodiment there is a pair of switches 24A, 28A and 24B, 28B associated with each cam actuator surface 20 so that oneswitch is closed in both the extended and depressed positions of the pushbuttons I0. The movable contacts 24A and 24B of each pair of switches may be formed out of a single strip of spring metal which is attached to the printed circuit board by a rivet shaped fastener 30 soldered to such board and to the intermediate portion of such spring contact member. Thus, both the movable contacts 24A and 24B and the fixed contacts 28A and 28B of the cam actuated switches are fixedly attached to the printed circuit board, thereby providing the switch with low lead inductance and enabling an extremely high frequency signal response, as discussed in copending application Ser. No. 765,597, referred to previously.

The switch actuators 18 are each engaged at their front end by an enlarged stop portion 32 on the pushbutton member 10 extending through a channel in such actuator, and are engaged at their rear end by a coil spring 34 surrounding the cylindrical rear portion of the pushbutton member. The spring 34 is compressed between the actuator and a seat portion on the interior of the housing 16, such seat portion surrounding the outlet opening in such housing through which the rear end of the pushbutton is depressed. When a pushbutton member is pushed into the depressed position to close the rear set of switch contacts 24A and 28A and to open the front set of switch contacts 248 and 28B, a spring biased latch bar 36 holds such pushbutton in such depressed position by engaging a latch portion 37 projecting from the side of the pushbutton. The latch bar 36 rotates about a pair of pivots 38 on its opposite ends extending through holes 39 in the opposite sides of the housing 16 and is resiliently biased into engagement with the pushbutton members 10 due to the rotational force of a coil spring 40 engaging a tab portion 42 of such latch bar. When another pushbutton is depressed, the latch projection 37 on such pushbutton member pivots the latch bar 36 until it releases the previously depressed pushbutton. This enables the coil spring 34 on such previously depressed pushbutton to return it to an extended position.

A plurality of lockout members 44 are provided in a row within a guide slot on the inner surface of the top of the housing 16. Each of the lockout members 44 is in the form of a flat, Y" shaped plate. A lockout cam projection 46 extends from the top of each of the actuator members 44 is in the form of a flat, Y" shaped plate. A lockout cam projection 46 extends from the top of each of the actuator members 18 into a position adjacent the space between two lockout members. When the pushbutton member is depressed, it slides the lockout projection 46 between two adjacent lockout members and moves them laterally apart to jam the lockout members together so that further lateral movement is not possible. As a result of the lockout action, when a second pushbutton member is depressed simultaneously with the first pushbutton, such second pushbutton member cannot be moved into the actuated depressed position because its associated lockout projection 46 engages one of the lockout members 44 and cannot slide between adjacent lockout members. This means that only one pushbutton at a time can be depressed to actuate its associated switch means. A similar lockout mechanism is shown in U.S. Pat. No. 3,271,530 mentioned previously.

The housing 16 containing the pushbutton switch apparatus is attached to the etched circuit board 26 by a pair of resilient plastic clip portions 48 which extend from the bottom of the housing and engage the opposite sides of such board. in addition, a plurality of guide posts 50 extend from the bottom of the housing 16 for engagement with corresponding holes in the circuit board to properly locate the switch actuators 18 with respect to the switch contacts 24, 28 on such board. This enables the pushbutton switch actuator means and associated apparatus to be quickly and easily removed from the printed circuit board to enable repair or replacement of such apparatus or the switch contacts on such board. The pushbutton switch apparatus may be attached to the front panel of a cathode-ray oscilloscope or other electronic instrument by means of a plurality of mounting plates 52 of metal provided within slots in the front of the housing-16 and having screw threaded holes in alignment with apertures extending through the housing wall between the pushbutton apertures.

As shown in FIGS. 1 and 4, the pushbuttons are illuminated when they are pushed into the depressed position lit) to move a rear end portion 54 of such depressed pushbutton into light-coupling relationship with the light guide 14. Thus the rear end portion 54 is moved through one of a plurality of shutter apertures in a shutter plate 56, which extends across the rear of the housing 16. A plurality of shutter doors 58 are provided over the shutter apertures to normally close such apertures. The shutter doors may be in the form of leaf spring members which are made integral with the metal shutter plate 56. However, it is also possible to make the shutter doors 58 as separate members secured directly to the housing 16 over the pushbutton apertures in such housing. The purpose of the shutter doors 58 is to prevent light from entering the pushbutton members 10 in their normal extended positions when the doors are closed, while enabling the selected push button 10' to open its door and move through the shutter aperture into a light-coupling relationship with the light guide member 14 in its depressed position.

The light guide 14 may be of a similar light transparent plastic material as the pushbutton members 10, and is provided with a plurality of branch portions 60, equal in number to the pushbutton members. Each of the light conducting branches 60 is provided with a light output end surface 62 which extends parallel to a light input surface 64 on the rear end 54 of each pushbutton member to enable light to be transmitted from the light guide into the pushbutton members. A single light source 66, such as an incandescent filament light bulb, is provided within a circular aperture in the light guide 14 so that light is transmitted from such source into the light guide. A portion of this light is transmitted through each of the light conducting branches 60 to their light output ends 62. It'

has been found that if the inputs of such branches are of the same size, the amount of light transmitted to the light outputs furthest from the light source is less than the light transmitted to light outputs closer to such source. This tends to cause the pushbuttons to be illuminated nonuniformly with different brightnesses. in order to compensate for this, the cross-sectional areas of the input ends of the light branches 60 are different with such areas being greaterfor branches having light outputs further from the light source, Thus, as shown in FIG. 4, when the light guide member 14 is of a uniform thickness, the widths 68 and 69 of the input ends of the two outer branches 60 are greater than the widths 70 of the input ends of the two inner branches. As a result, all of the pushbuttons are provided with a uniform brightness when they are illuminated in their depressed positions. In addition, since the shutter doors 58 prevent light from entering undepressed push buttons, there is a greater contrast between the illuminated and unilluminated pushbuttons.

The light guide member 14 and the light bulb 66 are secured to the housing 16 by a spring clip 72, whose opposite ends 74 are inserted into slots on the sides of the housing. in addition, such clip has two pairs of tab projections 76 to prevent lateral movement of the light guide and the light bulb. It should be noted that longitudinal movement of the light guide is prevented, since the edges at the output ends of the branches 60 engage the slot between the edge of the shutter door 58 and the shutter opening corresponding thereto. As a result, the light guide is fixed in position to insure accurate alignment of the light input surface 64 of the pushbutton, and the light output surface 62 of the light guide branch associated therewith when such pushbutton is depressed.

While the light bulb 66 may be directly soldered to the circuit board, a pair of lead conductors 78 provided as two separate insulated wires or as a single unit of two conductors on a flexible plastic strip, are employed to connect such light bulb to a pair of contacts on the edge of the circuit board. This provides more room for the electrical circuit on the etched circuit board. Since it is desirable that such light bulb is only illuminated when one of the pushbuttons is depressed, such light bulb can be connected into an electrical circuit controlled by the front switches or the rear switches of the cam actuated switch means associated with each pushbutton.

It should be noted that the light guide member may be molded into the shape shown and, as such, is provided with an extremely smooth, light reflecting outer surface so that no light reflecting coating is necessary. However, in some cases, such a light reflecting coating of white paint, aluminum or other suitable material may be provided on the surface of such light guide, except for the output surface portions 62 and the input surface portion surrounding the aperture containing the light bulb.

it will be obvious to those having ordinary skill in the art that many changes may be made in the above-described details of the preferred embodiment of the present invention without departing from the spirit of the invention. For example, the pushbutton illumination means can be employed with other types of switches than cam actuated switches. Therefore the scope of the present invention should only be determined by the following claims.

What we claim is:

1. Pushbutton switch apparatus comprising:

a plurality of pushbutton switch means each including a pushbutton member of light conducting material which moves between an extended position and a depressed position for operating an associated switch;

illumination means for selectively illuminating the pushbutton members when they are moved into the depressed position, said illumination means including at least one light source provided in light-coupling relationship to a light guide member having a plurality of light conducting branches with light output ends;

mounting means for mounting the light conducting branches in a fixed position behind the rear ends of the pushbutton members; and

means for selectively light coupling said output ends to said rear ends in response to movement of the pushbutton members so that in the depressed position, but not in the extended position, the pushbutton members have their rear ends in light coupling relationship with the output ends of corresponding branches of said light guide member to enable the transmission of light into said selected pushbutton member through its rear end.

2. The switch apparatus of claim 1 in which the light source is a light bulbprovided within an aperture in the light guide, and the light input ends of the light conducting branches are of different cross-sectional areas which increase in area for branches having their output ends a greater distance from the light bulb.

3. The switch apparatus of claim 2 in which the pushbutton members are arranged in a longitudinal row and the light bulb is energized through said switches only when a pushbutton member is depressed.

4. The switch apparatus of claim 1 which also includes a shutter means including light opaque shutter member provided between the light guide and the pushbutton members and having a plurality of apertures through which the pushbutton members are moved into their depressed positions, and a plurality of light opaque shutter doors closing said shutter apertures and extending between the output ends of the light guide branches and the input ends of the pushbutton members until said doors are moved open by a depressed pushbutton member.

5. The switch apparatus of claim 4 in which the shutter doors are leaf spring members formed integral with the shutter member out of a single sheet of metal.

6. Pushbutton switch apparatus comprising: a plurality of cam actuated switches each including at least one movable contact engaged by a cam actuator;

pushbutton means including a plurality of pushbutton members movable between an extended position and a depressed position, for moving the cam actuators of said switches to selectively operate said switches;

lock means holding the selected pushbutton member in the depressed position and releasing said selected pushbutton member and causing it to return to the extended position when another pushbutton member is depressed;

a circuit board having electrical circuit leads formed by insulated conductor strips provided thereon and having the movable contacts of said switches fixedly attached to said board and connected to said conductor strips; and

mounting means mounting said pushbutton members on one side of said circuit board to enable movement of the pushbutton members and their associated cam actuators substantially parallel to said circuit board.

7. The switch apparatus of claim 6 which also includes illumination means selectively illuminating the pushbutton members which are made of light conducting material when they are depressed into a switch operating position, said illumination means including a single light source and a light guide member mounted behind the rear ends of said pushbutton members with a plurality of light conducting branches of said light guide member extending to light output ends positioned adjacent the depressed positions of said rear ends of the pushbutton members.

8. The switch apparatus of claim 7 in which the light input ends of said branches have different areas which increase in area for branches having their output ends a greater distance from the light source.

9. A switching device comprising:

mounting means;

a plurality of selectively operated pushbutton means of light conductive material disposed in said mounting means for selective movement relative thereto between one position and another position;

movable contact means disposed along said mounting means adjacent said pushbutton means;

stationary contact means provided in alignment with said movable contact means;

cam means on said pushbutton means for engagement with said movable contact means for moving said movable contact means into and out of engagement with said stationary contact means;

locking means between said mounting means and said pushbutton means for locking one of said pushbutton means in the one position defining a contact-operating position, and for releasing another of said pushbutton means when said one pushbutton means is moved to said one position; and

illumination means for selectively transmitting light through inner ends of said pushbutton means when the selected pushbutton means has been moved to said contactoperating position and into light-coupling relationship with said illumination means thereby illuminating an outer end of said selected pushbutton means.

10. A switching device according to claim 9 wherein said illumination means comprise a light guide having light-conducting branches with light output ends, light source means disposed within an opening in said light guide, said light-conducting branches having different cross-sectional areas which increase in area with the distance from the light source means.

11. A switching device according to claim 9 wherein shutter means is positioned adjacent said illumination means and having apertures through which the inner-ends of said pushbutton means extend when in said contact-operating position, and shutter means closing said apertures when said pushbutton means are in said another position. 

1. Pushbutton switch apparatus comprising: a plurality of pushbutton switch means each including a pushbutton member of light conducting material which moves between an extended position and a depressed position for operating an associated switch; illumination means for selectively illuminating the pushbutton members when they are moved into the depressed position, said illumination means including at least one light source provided in light-coupling relationship to a light guide member having a plurality of light conducting branches with light output ends; mounting means for mounting the light conducting branches in a fixed position behind the rear ends of the pushbutton members; and means for selectively light coupling said output ends to said rear ends in response to movement of the pushbutton members so that in the depressed position, but not in the extended position, the pushbutton members have their rear ends in light coupling relationship with the output ends of corresponding branches of said light guide member to enable the transmission of light into said selected pushbutton member through its rear end.
 2. The switch apparatus of claim 1 in which the light source is a light bulb provided within an aperture in the light guide, and the light input ends of the light conducting branches are of different cross-sectional areas which increase in area for branches having their output ends a greater distance from the light bulb.
 3. The switch apparatus of claim 2 in which the pushbutton members are arranged in a longitudinal row and the light bulb is energized through said switches only when a pushbutton member is depressed.
 4. The switch apparatus of claim 1 which also includes a shutter means including light opaque shutter member provided between the light guide and the pushbutton members and having a plurality of apertures through which the pushbutton members are moved into their depressed positions, and a plurality of light opaque shutter doors closing said shutter apertures and extending between the output ends of the light guide branches and the input ends of the pushbutton members until said doors are moved open by a depressed pushbutton member.
 5. The switch apparatus of claim 4 in which the shutter doors are leaf spring members formed integral with the shutter member out of a single sheet of metal.
 6. Pushbutton switch apparatus comprising: a plurality of cam actuated switches each including at least one movable contact engaged by a Cam actuator; pushbutton means including a plurality of pushbutton members movable between an extended position and a depressed position, for moving the cam actuators of said switches to selectively operate said switches; lock means holding the selected pushbutton member in the depressed position and releasing said selected pushbutton member and causing it to return to the extended position when another pushbutton member is depressed; a circuit board having electrical circuit leads formed by insulated conductor strips provided thereon and having the movable contacts of said switches fixedly attached to said board and connected to said conductor strips; and mounting means mounting said pushbutton members on one side of said circuit board to enable movement of the pushbutton members and their associated cam actuators substantially parallel to said circuit board.
 7. The switch apparatus of claim 6 which also includes illumination means selectively illuminating the pushbutton members which are made of light conducting material when they are depressed into a switch operating position, said illumination means including a single light source and a light guide member mounted behind the rear ends of said pushbutton members with a plurality of light conducting branches of said light guide member extending to light output ends positioned adjacent the depressed positions of said rear ends of the pushbutton members.
 8. The switch apparatus of claim 7 in which the light input ends of said branches have different areas which increase in area for branches having their output ends a greater distance from the light source.
 9. A switching device comprising: mounting means; a plurality of selectively operated pushbutton means of light conductive material disposed in said mounting means for selective movement relative thereto between one position and another position; movable contact means disposed along said mounting means adjacent said pushbutton means; stationary contact means provided in alignment with said movable contact means; cam means on said pushbutton means for engagement with said movable contact means for moving said movable contact means into and out of engagement with said stationary contact means; locking means between said mounting means and said pushbutton means for locking one of said pushbutton means in the one position defining a contact-operating position, and for releasing another of said pushbutton means when said one pushbutton means is moved to said one position; and illumination means for selectively transmitting light through inner ends of said pushbutton means when the selected pushbutton means has been moved to said contact-operating position and into light-coupling relationship with said illumination means thereby illuminating an outer end of said selected pushbutton means.
 10. A switching device according to claim 9 wherein said illumination means comprise a light guide having light-conducting branches with light output ends, light source means disposed within an opening in said light guide, said light-conducting branches having different cross-sectional areas which increase in area with the distance from the light source means.
 11. A switching device according to claim 9 wherein shutter means is positioned adjacent said illumination means and having apertures through which the inner-ends of said pushbutton means extend when in said contact-operating position, and shutter means closing said apertures when said pushbutton means are in said another position. 